TapTap
423a62e691
Three receiver security fixes from the audit: 1. --temp-dir symlink escape (High): file_open_temp_dir() opened the client-controlled scratch dir with a bare open(), so a symlink planted under the receive root let a peer redirect receiver scratch files outside the authorized root. The opened dir is now judged by the REAL path of its fd (via /proc/self/fd), and any target outside the authorized receive root is refused with a logged error (EACCES). An in-root symlink (the EXDEV cross-filesystem fallback case) still works, and the no-root local batch path is unchanged. 2. setuid/setgid/sticky under SUPER_MODE_OFF (High): the special bits were applied under --perms (and via --chmod) even when the connection forbade super-user activities. FileAttrPolicy gains super_permitted, set by file_attr_policy_from_config() from privilege_super_mode_permitted(); metadata_mode_for_policy(), the symlink path, the special-node creation path, and the deferred directory-mode apply now strip the special bits when it is false. Exact rsync semantics are preserved when permitted. 3. daemon umask (Low): daemonize() forced umask(0), so implied parent directories created without -p were world-writable 0777. Set the conventional daemon umask 022 instead (rsync never forces 0); -p/-a mode preservation is unaffected because it restores modes via fchmod. Tests: new unit tests for file_open_temp_dir confinement and the masked/unmasked special-bit policy (incl. the --chmod path), a daemon world-writable-dir regression test, an integration escape test, and a root-only integration test asserting special bits are masked without --allow-super. The old cross-filesystem test encoded the vulnerable behavior (symlink target outside the root) and is replaced by the escape test; the EXDEV fallback code is retained for in-root links.
204 lines
13 KiB
C
204 lines
13 KiB
C
#ifndef FILE_H
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#define FILE_H
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#include "file_send.h"
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#include "file_receive.h"
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#include "file_types.h"
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#include "checksum.h"
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#include <stdbool.h>
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#include <stdint.h>
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#include <sys/stat.h>
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/* File/FileMetadata lifecycle, local disk helpers, and secure filesystem
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primitives shared by the send/receive pipelines. */
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File* file_create(const char* path);
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void file_destroy(void* item);
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bool file_load_data(File* file);
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/* Compute the whole-file content digest of `file` with the negotiated
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* --checksum-choice algorithm and --checksum-seed. Writes the digest into
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* `out` (capacity `out_capacity`) and its length into `*out_len`. Returns
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* false on read/allocation failure or when the digest would not fit. */
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bool file_checksum(File* file, ChecksumAlgo algo, uint64_t seed, uint8_t* out, size_t out_capacity,
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size_t* out_len);
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size_t file_content_to_buffer(File* file);
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FileMetadata* file_metadata_create(const char* path, const struct stat* stats, bool capture_atime,
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bool capture_crtime);
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void file_metadata_destroy(void* metadata);
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/* --open-noatime process-wide sender policy; see file.c. */
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void file_set_open_noatime(bool enable);
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bool file_get_open_noatime(void);
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/* Capture the process umask ONCE, before any threads are created. Call this at
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* the very top of main() in both entry points so the cached value is read while
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* the process is still single-threaded: reading the umask needs a get+set round
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* trip (umask(0); umask(old)), which would race against receiver threads
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* creating files if it happened during the first write. Idempotent and safe to
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* call more than once. */
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void file_umask_capture(void);
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/* Process-wide umask, captured once (thread-safe). Used to derive the mode of
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* a brand-new destination like rsync: source_mode & 0777 & ~umask. Falls back
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* to file_umask_capture() (behind pthread_once) if capture was never called. */
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unsigned file_process_umask(void);
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/* Open `path` read-only for transfer, honouring --open-noatime when set. */
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int file_open_for_read(const char* path);
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bool file_write_to_disk(const char* path, const void* data, unsigned long long data_size,
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bool inplace, bool sparse);
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/* Symlink trust-boundary helpers (Phase 4, symlink wave; rsync parity).
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* --munge-links is a RECEIVER-side rewrite: rsync prefixes every stored symlink
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* target with this marker, making the link unusable while the referenced
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* directory does not exist. A SENDER receiving a munged source strips it back
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* off before transmitting (so a munged tree round-trips through the receiver's
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* re-munging). */
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#define SYMLINK_MUNGE_PREFIX "/rsyncd-munged/"
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char* file_symlink_munge(const char* target);
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/* rsync 3.4.1 unsafe_symlink(): true when `target` escapes the transfer tree
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* rooted at `link_path` (the symlink's transfer-relative path incl. its name).
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* Absolute/empty targets and targets climbing above the transfer root (via
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* "..") are unsafe, as are internal "/../" components and trailing "/..". */
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bool file_symlink_unsafe(const char* target, const char* link_path);
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/* True when a lexical target is relative and contains no ".." component, so it
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* can never escape the receive root once created beneath it. */
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bool file_symlink_target_contained(const char* target);
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/* Strip a leading SYMLINK_MUNGE_PREFIX from `target` (mutable, in place);
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* returns true when a marker was removed. */
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bool file_symlink_unmunge(char* target);
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/* Create a symlink at `path` -> `target`, confined below the authorized root
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* (O_NOFOLLOW parent walk, symlinkat; the target is never followed). The link
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* value is copied verbatim (rsync -l); only the placement path is confined.
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* Returns false when a directory already occupies `path`. */
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bool file_symlink_at_secure(const char* path, const char* target);
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/* --keep-dirlinks (-K) receiver process-wide policy: allow an in-root existing
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* symlink-to-directory to be followed as a directory. */
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void file_set_keep_dirlinks(bool enable);
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/* --trust-sender receiver process-wide policy (Phase 5). When set, the
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* receiver trusts that the sender already produced a clean file list and skips
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* its own redundant up-front re-validation of incoming paths (the empty/".."
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* rejection and the escaping-symlink-target containment). The low-level
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* fd-relative confinement primitives below are deliberately NOT disabled by
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* this flag, so a hostile sender still cannot escape the authorized root. */
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void file_set_trust_sender(bool enable);
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bool file_get_trust_sender(void);
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/* Secure path/filesystem primitives (symlink-safe, O_NOFOLLOW, root-confined). */
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bool file_path_exists_secure(const char* path);
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bool file_stat_secure(const char* path, struct stat* st);
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bool file_destination_is_newer_secure(const char* path, const FileMetadata* metadata);
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int file_open_secure_parent(const char* path, char** leaf_out, bool create_dirs);
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/* Protocol 2.28.0 variant: also increments *dirs_created for every missing
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* parent directory this walk creates that lies strictly below `count_floor`
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* (a receive-root-relative path, or NULL to count all of them). */
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int file_open_secure_parent_counted(const char* path, char** leaf_out, bool create_dirs,
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unsigned* dirs_created, const char* count_floor);
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bool file_ensure_directory_secure(const char* path);
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bool file_directory_exists_secure(const char* path);
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bool file_rename_secure(const char* old_path, const char* new_path);
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/* Remove the whole directory tree at `path` (confined, symlink-safe). Used by
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--force to clear a non-empty destination directory that blocks an incoming
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regular file. See the .c for the exact success semantics. */
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bool file_remove_tree_secure(const char* path);
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/* Open a private 0700 directory (creating it on demand) that must live below
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the authorized root. Used for the --delay-updates staging directory. */
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int file_open_private_dir(const char* dir_path);
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/* Open an existing --temp-dir scratch directory (relative or absolute; no
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creation). When an authorized receive root is configured the directory's
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REAL path (symlinks resolved) must lie within it, so a client-planted
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symlink cannot redirect receiver scratch files outside the sandbox; an
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in-root symlink to another filesystem is still allowed for rsync's EXDEV
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fallback. */
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int file_open_temp_dir(const char* dir_path);
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/* The file_to_disk_secure* variants write a temporary copy in the destination
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directory and atomically rename it over `path`. temp_dir is a scratch
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directory (an absolute path, or one the caller already resolved against the
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destination root): when it is non-NULL the temporary copy is instead created
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there (with a name unique across the whole scratch directory) and atomically
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renamed into the destination directory once fully written and fsynced. When
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that rename/link fails with EXDEV (the scratch dir is on another filesystem)
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the write falls back to a non-atomic copy directly in the destination
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directory, matching rsync. Pass NULL for the same-directory behavior.
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--inplace writes never use temp_dir. */
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bool file_to_disk_secure(const char* path, const void* data, unsigned long long data_size,
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bool inplace, bool sparse, bool preallocate, const FileMetadata* metadata,
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FileAttrPolicy policy, const char* temp_dir);
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bool file_to_disk_secure_with_fsync(const char* path, const void* data,
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unsigned long long data_size, bool inplace, bool sparse,
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bool preallocate, const FileMetadata* metadata,
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FileAttrPolicy policy, bool use_fsync, const char* temp_dir);
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/* With update enabled, an existing newer destination is left untouched. The
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check is descriptor-based for inplace writes; atomic replacement still has
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an unavoidable final rename race without filesystem locking. */
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bool file_to_disk_secure_update(const char* path, const void* data, unsigned long long data_size,
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bool inplace, bool sparse, bool preallocate,
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const FileMetadata* metadata, FileAttrPolicy policy,
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const char* temp_dir);
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bool file_to_disk_secure_no_replace(const char* path, const void* data,
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unsigned long long data_size, bool sparse, bool preallocate,
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const FileMetadata* metadata, FileAttrPolicy policy,
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const char* temp_dir);
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/* Receiver write-path variant that also applies per-file xattrs (-X/-A) and the
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* --fake-super stat xattr fd-relative before the final rename. `update` /
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* `no_replace` / `use_fsync` mirror the plain wrappers above; `keep_partial`
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* enables --partial best-effort retention of a failed write's temp. */
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bool file_to_disk_secure_attrs(const char* path, const void* data, unsigned long long data_size,
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bool inplace, bool sparse, bool preallocate,
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const FileMetadata* metadata, FileAttrPolicy policy, bool update,
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bool no_replace, bool use_fsync, const FileXattrList* xattrs,
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bool fake_super, bool keep_partial, const char* temp_dir);
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/* Atomic --link-dest install: replace `path` with a hard link to `basis_path`
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(via a temp name + rename); fall back to a byte-identical local copy from
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`data` when the link is impossible (EXDEV/EPERM/unsupported filesystem).
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`metadata` is applied only on the copy fallback. `preallocate` applies to
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that copy fallback only (a hard-linked file shares the basis inode and is
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never re-allocated). */
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bool file_to_disk_secure_link(const char* path, const char* basis_path, const void* data,
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unsigned long long data_size, bool preallocate,
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const FileMetadata* metadata, FileAttrPolicy policy, bool use_fsync,
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const char* temp_dir);
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/* Like file_to_disk_secure_link, but the byte-copy fallback also applies the
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* per-file xattrs (-X/-A) and --fake-super stat xattr (fd-relative). On a
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* successful hard link no attributes are applied (the shared inode already
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* carries the basis's). */
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bool file_to_disk_secure_link_attrs(const char* path, const char* basis_path, const void* data,
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unsigned long long data_size, bool preallocate,
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const FileMetadata* metadata, FileAttrPolicy policy,
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bool use_fsync, const FileXattrList* xattrs, bool fake_super,
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const char* temp_dir);
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/* Streaming --copy-dest install: atomically materialize `path` by copying the
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* bytes of `basis_path` through a bounded buffer (no whole-file buffering, so
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* an arbitrarily large basis works), applying the SOURCE metadata and the
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* per-file xattrs / --fake-super record. `update` honors a newer destination;
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* a --temp-dir scratch location falls back to a direct write on EXDEV. */
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bool file_copy_basis_stream_attrs(const char* path, const char* basis_path,
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unsigned long long expected_size, bool preallocate,
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const FileMetadata* metadata, FileAttrPolicy policy, bool update,
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bool use_fsync, const FileXattrList* xattrs, bool fake_super,
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const char* temp_dir);
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/* Protocol 2.28.0 receiver-stat variants: like the two above but additionally
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* report through `dirs_created` (when non-NULL) how many parent directories the
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* confined secure walk had to create that lie strictly below `count_floor` (a
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* receive-root-relative prefix, or NULL for all). Used to reproduce rsync's
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* `Number of created files` directory count on a fresh destination. */
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bool file_to_disk_secure_attrs_counted(const char* path, const void* data,
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unsigned long long data_size, bool inplace, bool sparse,
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bool preallocate, const FileMetadata* metadata,
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FileAttrPolicy policy, bool update, bool no_replace,
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bool use_fsync, const FileXattrList* xattrs, bool fake_super,
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bool keep_partial, const char* temp_dir,
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unsigned* dirs_created, const char* count_floor);
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bool file_to_disk_secure_link_attrs_counted(const char* path, const char* basis_path,
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const void* data, unsigned long long data_size,
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bool preallocate, const FileMetadata* metadata,
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FileAttrPolicy policy, bool use_fsync,
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const FileXattrList* xattrs, bool fake_super,
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const char* temp_dir, unsigned* dirs_created,
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const char* count_floor);
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/* The logical transfer root expressed receive-root-relative, or NULL when the
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* wire paths carry no mirror scaffolding above it. Caller frees non-NULL. */
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char* file_transfer_root_floor(const Config* config);
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#endif
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